Revert "drop book.rake"
Revert "drop book.rake"

This reverts commit 495fa431d30524a0a9c2cf617d29d42d427f9414.

Even though we don't run `remote_genbook` as part of the
cron setup, it is still potentially useful for re-loading v1
book translations. Let's leave it.

git/git-scm.com,mosoft521/gitscm-next,jasonlong/git-scm.com,mosoft521/gitscm-next,Mokolea/git-scm.com,git/git-scm.com,Mokolea/git-scm.com,jasonlong/git-scm.com,mosoft521/gitscm-next,mosoft521/gitscm-next,git/git-scm.com,jasonlong/git-scm.com,git/git-scm.com,jasonlong/git-scm.com,Mokolea/git-scm.com,Mokolea/git-scm.com